/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.transforms;



import com.bff.gaia.unified.sdk.annotations.Internal;

import com.bff.gaia.unified.sdk.values.PCollection;

import com.bff.gaia.unified.sdk.values.PCollectionView;



import java.io.Serializable;



/**

 * <b><i>For internal use only; no backwards-compatibility guarantees.</i></b>

 *

 * <p>A function to adapt a primitive "view" of a {@link PCollection} - some materialization

 * specified in the Unified model and implemented by the runner - to a user-facing view type for side

 * input.

 *

 * <p>Both the underlying primitive view and the user-facing view are immutable.

 *

 * <p>The most common case is using the {@link View} transforms to prepare a {@link PCollection} for

 * use as a side input to {@link ParDo}. See {@link View#asSingleton()}, {@link View#asIterable()},

 * and {@link View#asMap()} for more detail on specific views available in the SDK.

 *

 * @param <PrimitiveViewT> the type of the underlying primitive view required

 * @param <ViewT> the type of the value(s) accessible via this {@link PCollectionView}

 */

@Internal

public abstract class ViewFn<PrimitiveViewT, ViewT> implements Serializable {

  /** Gets the materialization of this {@link ViewFn}. */

  public abstract Materialization<PrimitiveViewT> getMaterialization();



  /** A function to adapt a primitive view type to a desired view type. */

  public abstract ViewT apply(PrimitiveViewT primitiveViewT);

}